I did some testing with the stock psu vs. an atx psu. short story: no effect on hash rate or hard errors, etc. multiple furys use less power with one atx psu vs. several stock psu. if you want to read the whole write up...

http://www.techunboxed.com/2014/07/gaw-miners-fury-power-supply-mod.html

let me know what you think.